DETECTION OF HC11N IN THE COLD DUST CLOUD TMC-1

Two consecutive rotational transitions of the long cyanopolyyne HC11N, J = 39 --> 38 and 38 --> 37, have been detected in the cold dust clou d TMC-1 at the frequencies expected from recent laboratory measurement s by Travers and coworkers, and at about the expected intensities. The astronomical lines have a mean radial velocity of 5.8(1) km s(-1), in good agreement with the shorter cyanopolyynes HC7N and HC9N observed in this very sharp line source [5.82(5) and 5.84(5) km s(-1), respecti vely]. The column density of HC,,N is calculated to be 2.8 x 10(11) cm (-2). The abundance of the cyanopolyynes decreases smoothly with lengt h to HC11N, the decrement from one to the next being about six for the longer carbon chains.